The present invention relates to stabilizers for light sensitive diazonium compounds and to presensitized reproduction materials such as lithographic plates having improved stability to the action of heat/or and moisture.
Presensitized reproduction materials used as used for planographic printing processes generally comprise a plate base or support member having a subbase coating or layer, over which is applied a photosensitive coating composition. The plate base may be a flexible sheet such as paper, plastic or metal which is treated to provide a hydrophilic or otherwise prepared surface upon which a photosensitive coating will adhere. In the case of metal plates, aluminum sheeting is most commonly employed as the base material having a grained or etched surface and/or a subbase formed by silica based coatings or by anodization of the aluminum in acidic electrolytic baths.
Diazonium compounds most commonly employed in the preparation of light sensitive compositions suitable for lithographic plate applications or photoresist applications may be characterized by the generic structure A--N.sub.2.sup.+ X.sup.-, wherein A is an aromatic or heterocylic residue and X is the anion of an acid.
Specific examples of light sensitive diazonium materials useful as aforementioned include higher molecular weight compositions obtained, for example, by the condensation of certain aromatic diazonium salts in an acid condensation medium with active carbonyl compounds such as formaldehyde, as disclosed for example in U.S. Pat. Nos. 2,063,631 and 2,667,415.
More recently, improved diazonium materials within the above generic formula have been developed which are faster, more adherable to support materials and exhibit lessened sensitivity to moisture. These include the reaction products having the composition of Formula I.
FORMULA I: PA1 condensed with: PA1 at least one compound of the general formula EQU R(--CH.sub.2 --OR.sub.2).sub.n PA1 wherein n is an integer from 1 to 4, R is a residue produced by the splitting off of n hydrogen atoms from a diphenyl ether, and R.sub.2 is an alkyl group with 1 to 4 carbon atoms, said condensation product containing, on the average, 0.25 to 0.75 unit derived from R(--CH.sub.2 --OR.sub.2).sub.n per diazo group. PA1 FORMULA II: PA1 and ##STR2## wherein R.sub.1 is an aryl group of the benzene or napthalene series PA1 R'.sub.1 is an arylene group of the benzene or napthalene series PA1 R.sub.2 is a phenylene group PA1 R.sub.3 is a single bond or one of the groups EQU --(CH.sub.2).sub.q --NR.sub.4 -- EQU --O--(CH.sub.2)--NR.sub.4 -- EQU --S--(CH.sub.2).sub.r --NR.sub.4 -- EQU --S--CH.sub.2 --CO--NR.sub.4 -- EQU --O--R.sub.5 --O-- EQU --O-- EQU --S-- or --CO--NR.sub.4 -- PA1 the left-hand free valence of the specified groups is attached to R.sub.1 and the right-hand valance is attached to R.sub.2 PA1 wherein PA1 q is a number from 0 to 5 PA1 r is a number from 2 to 5 PA1 R.sub.4 is selected from the group consisting of hydrogen, alkyl with 1 to 5 carbon atoms, aralkyl with 7 to 12 carbon atoms, and aryl with 6 to 12 carbon atoms, PA1 R.sub.5 is an arylene group having 6 to 12 carbon atoms PA1 Y is one of the groups --NH--, and --O-- PA1 X is an anion PA1 P is a number from 1 to 3 PA1 E is a residue obtained by splitting off m H atoms from a compound free of diazonium groups selected from the group consisting of aromatic amines, phenols, thiophenols, phenol ethers, aromatic thioethers, aromatic heterocyclic compounds, aromatic hydrocarbons and organic acid amines, PA1 R.sub.a is selected from the group consisting of hydrogen and phenyl, PA1 R.sub.b is selected from the group consisting of hydrogen and alkyl and acyl groups having 1 to 4 carbon atoms, and a phenyl group, and PA1 m is an integer from 1 to 10, PA1 are reacted in a strongly acid condensation medium and under condensation conditions sufficient to produce a polycondensation product of an aromatic diazonium compound containing, on the average, about 0.1 to 50 B.sub.1 units per unit of A--N.sub.2 X. PA1 FORMULA III: PA1 and ##STR3## wherein R.sub.1 is an arylene group of the benzene or naphthalene series PA1 R.sub.2 is a phenylene group PA1 R.sub.3 is a single bond or one of the groups EQU --(CH.sub.2).sub.q --NR.sub.4 -- EQU --O--(CH.sub.2).sub.r --NR.sub.4 -- EQU --S--(CH.sub.2).sub.r --NR.sub.4 -- EQU --S--(CH.sub.2).sub.r --CO--NR.sub.4 -- EQU --O--R.sub.5 --O-- EQU --O-- EQU --S-- or EQU --CO--NR.sub.4 -- PA1 the left-hand free valence of the specified groups is attached to R.sub.1 and the right-hand free valence is attached to R.sub.2 PA1 wherein PA1 q is a number from 0 to 5 PA1 r is a number from 2 to 5 PA1 R.sub.4 is selected from the group consisting of hydrogen, alkyl with 1 to 5 carbon atoms, aralkyl with 7 to 12 carbon atoms, and aryl with 6 to 12 carbon atoms, PA1 R.sub.5 is an arylene group having 6 to 12 carbon atoms --Y-- is one of the groups --NH--, and --O--, PA1 X is the anion of the diazonium compound, and PA1 p is a number from 1 to 3, and PA1 B is a radical of a compound selected from the group consisting of aromatic amines, phenols, thiophenols, phenol ethers, aromatic thioethers, aromatic hetercyclic compounds, aromatic hydrocarbons and organic acid amides, in which the aromatic nuclei are unsubstituted or substituted by at least one substituent activating condensation and selected from the group consisting of --NR.sub.7 R.sub.8, --N(R.sub.8).sub.2, --OR.sub.7, --OR.sub.8, --R.sub.8, and --SR.sub.8, PA1 wherein PA1 R.sub.7 is --H, --CO--alkyl, --CO--aryl, --SO.sub.2 --alkyl, --SO.sub.2 --aryl, --COHN.sub.2, or --CSNH.sub.2, and PA1 R.sub.8 is --H, --alkyl, --aryl or --aralkyl, the alkyl groups having 1 to 10, the aryl groups 6 to 20 and the arallkyl groups 7 to 20 carbon atoms, PA1 which diazonium compound contains, on the average, about 0.01 to 50 B units per unit of A--N.sub.2 X. PA1 FORMULA IV: PA1 m is 1 to about 9; PA1 Y is selected from the group consisting of --CH.sub.2 -- and --CH.sub.2 OCH.sub.2 --; and PA1 T is the same as R when Y is --CH.sub.2 -- and is hydrogen when Y is --CH.sub.2 --O--CH.sub.2 --, PA1 K is selected from the group consisting of ##STR7## --S--, --O--, and --CH.sub.2 --, or is absent; P and P.sub.1 are selected from the group consisting of C.sub.1 to C.sub.4 alkyl, methoxy, ethoxy, butoxy, and H; PA1 P.sub.1 may be the same as P or different; and PA1 X is an anion.
At least one diazonium salt having the structure: ##STR1## wherein R.sub.1 is selected from the group consisting of H, an alkoxy group having from 1 to 4 carbon atoms, and a 2-hydroxy-ethoxy group, and X is the anion of the diazonium salt,
Such materials are disclosed in U.S. Pat. No. 3,679,419, incorporated herein by reference.
Other diazonium compound condensation products include the polycondensation products having the composition of Formula II.
At least one A--N.sub.2.sup.+ X.sup.- compound condensed with at least one compound of the formula E(CHR.sub.a --OR.sub.b).sub.m in which A--N.sub.2 X is a radical of a compound selected from the group consisting of a compound of the formula EQU (R.sub.1 --R.sub.3).sub.p R.sub.2 --N.sub.2 X
Still other diazonium compound condensation products include those materials having repeating units of the composition of Formula III.
At least one A--N.sub.2.sup.+ X.sup.- compound condensed with at least one compound of the structure B, comprising repeating units of each of the general types A--N.sub.2 X and B which are linked by methylene groups, in which A--N.sub.2 X is a radical of a compound of one of the general formulae EQU (R.sub.1 --R.sub.3 --).sub.p R.sub.2 --N.sub.2 X
Yet another category of extremely fast light sensitive diazonium compound condensation products are those disclosed in co-pending application Ser. No. 06/359,335, filed in the U.S. Patent Office on Mar. 18, 1982, which is a continuation-in-part of Ser. No. 06/245,837, filed in the U.S. Patent Office on Mar. 20, 1981. These materials may be characterized by the composition of Formula IV.
The condensation product of oligomers having the structure: ##STR4## wherein: R is selected from the group consisting of ##STR5## n is an integer from 0 to 3; M is an aromatic radical of one or more compounds selected from the group consisting of aromatic hydrocarbons, diaryl ethers, diaryl sulfides, diaryl amines, diaryl sulfones, diaryl ketones and diaryl diketones;
with diazonium salts having the structure: ##STR6## wherein: R' is selected from the group consisting of phenyl and C.sub.1 to C.sub.4 alkyl substituted phenyl;
Whereas recently developed, faster diazonium compound condensation products offer many advantages in terms of speed and quality which render them extremely suitable in applications requiring low energy light exposure, including laser exposure applications, a major drawback is their decreased stability to heat. Whereas many of the less sensitive low molecular weight diazos exhibit a shelf life of weeks or months, under normal storage conditions, sensitized printing plates coated with the newer materials have a shelf life measured in hours, especially at higher storage temperatures approaching 100.degree. C.
Examples of prior art materials which are known diazo stabilizers in planographic printing plate applications include aryl and haloaryl sulfonic acids as taught in U.S. Pat. No. 2,649,373; phosphoric and sulfonic acids as taught in U.S. Pat. No. 3,679,419; benzophenone compounds as disclosed in U.S. Pat. No. 3,503,330; and diazo-borofluoride salts as taught in U.S. Pat. No. 3,933,499. U.S. Pat. No. 4,172,729 discloses a presensitized diazo lithographic plate having improved shelf life and printing performance containing up to 5% by weight of oxalic acid or a salt thereof as a stabilizer. The patent also comparatively recites the utilization of other additives such as citric, phosphoric, sulfonic, boric, sulfuric, polyphosphoric, adipic, sulfamic and tartaric acids as well as glycine and other acid salts.
Stabilizers have also been employed in two component light sensitive diazotype photographic compositions. These compositions are used in photographic processes where dyes are formed in-situ as the result of a coupling reaction between an undecomposed diazonium salt and a coupling component. The object of stabilization in these systems is to inhibit premature coupling of the diazonium salt and coupler during storage and prior to use. While the chemistry in such systems differs from the planographic systems disclosed herein, stabilizers similar to those employed in planographic systems have been suggested by the prior art.
Examples of such prior art stabilizers include aryl and haloaryl sulfonic acids and their salts as taught in U.S. Pat. No. 3,102,812; certain unsaturated organic acids such as crotonic, pentenic, sulfo cinnamic and derivatives of acrylic acid as taught in U.S. Pat. No. 2,354,088; certain anthranilic acids as taught in U.S. Pat. No. 2,496,240; certain acids such as tartaric, citric, boric, phosphoric and polyphosphoric such as taught in U.S. Pat. No. 3,615,574; certain acids including maleic, malonic, trichloroacetic, glyoxilic and sulfanilic as disclosed in U.S. Pat. No. 3,660,581; boric acid ester as disclosed in U.S. Pat. No. 3,679,421; certain organic acid amides, ketoacids, cyanoacids, cyclic acid derivatives, nitro acids and acetylenic acids as disclosed in U.S. Pat. No. 3,453,112; aromatic amines as disclosed U.S. Pat. No. 3,704,129; and saturated and unsaturated gamma lactones as disclosed in U.S. Pat. No. 2,374,563.
Whereas many of the aforementioned acid stabilizers might be considered suitable for the stabilization of any diazonium composition, it has been found that many of these acids affect the light sensitivity and speed of the diazonium composition. This is of particular disadvantage in the case of diazonium compound condensation products having the Formulas I through IV above since the enhancement of stability of such materials at the expense of speed and light sensitivity would render them of decreased utility in those applications where speed is of critical importance.
Accordingly, it is an object of this invention to provide light sensitive diazonium compound condensation product compositions having enhanced stability against heat and/or moisture and improved shelf life.
Another object is to provide light sensitive diazonium compound condensation product based photoresist materials and printing plates having enhanced stability and shelf life.
Another object is to impart increased shelf life to fast acting diazonium compound condensation product sensitized printing plates without a significant sacrifice of the speed of the diazonium compound condensation product.